Patent Application
20240190789
This patent document relates to material processing and engineering, and specifically to materials useful for energy storage.
Various nanoscale metals and metalloids have been explored as high-energy fuels in nanoenergetic composites for propellant and pyrotechnic applications.
One aspect of the disclosure provided herein relates to a composition comprising magnesium nanoparticles, a nanoscale metal or metalloid, and an oxidizer. When compared to a second composition comprising the same amount of the oxidizer and the nanoscale metal or metalloid but without the magnesium nanoparticles, the composition may have one or more advantages selected from the following: a) a reduced burn time (e.g., reduced by about 50% to about 70%, and/or by about 2.0 ms to about 5.0 ms); b) an increased pressurization rate (e.g., increased by about 5-fold to about 6-fold); c) an increased peak pressure (e.g., increased by about 15% to about 30%); and d) a lower ignition temperature (e.g., lower by about 50° C. to about 200° C., and/or an ignition temperature of about 500° C. to about 750° C.).
Examples of the Metal or Metalloid Include, without Limitation, Boron, Silicon, Aluminum, and Titanium.
In some embodiments, the oxidizer comprises a first oxide of the metal or metalloid. For example, the first oxide of the metal or metalloid may be a native oxide shell of the metal or metalloid. In other examples, the first oxide of the metal or metalloid may further comprise oxides that are not the native oxide shell of the metal or metalloid.
In some embodiments, the oxidizer comprises one or more second oxides other than the oxides of the metal or metalloid. Examples of the one or more second oxides include, without limitation, CuO, B2O3, SiO2, TiO2, and Al2O3.
In some embodiments, the oxidizer may be oxygen.
In some embodiments, the nanoscale metal or metalloid has an average particle size of about 100 nm to about 900 nm, or about 390 nm to about 420 nm.
In some embodiments, the magnesium nanoparticles have an average particle size of about 100 nm to about 900 nm, or about 350 nm to about 400 nm.
In some embodiments, the molar of the magnesium nanoparticles over the total molar of the magnesium nanoparticles and the nanoscale metal or metalloid is no more than about 30%, no more than about 25%, no more than about 20%, nor more than about 15%, no more than about 10%, or about 3.0% to about 15.0%.
In some embodiments, the molar ratio of the nanoscale metal or metalloid over the oxidizer is about +/−20% of the stoichiometric ratio. In some embodiments, the molar ratio of the nanoscale metal or metalloid over the total molar of one or more second oxides is about +/−20% of the stoichiometric ratio.
In some embodiments, the molar ratio of the magnesium nanoparticles and nanoscale metal or metalloid over the oxidizer is about +/−20% of the stoichiometric ratio. In some embodiments, the molar ratio of the magnesium nanoparticles and nanoscale metal or metalloid over the total molar of one or more second oxides is about +/−20% of the stoichiometric ratio.
In some embodiments, the molar ratio of the oxidizer over the nanoscale metal or metalloid is about +/−20% of the stoichiometric ratio. In some embodiments, the molar ratio of the total molar of one or more second oxides over the nanoscale metal or metalloid is about +/−20% of the stoichiometric ratio.
In some embodiments, the molar ratio of the oxidizer over the magnesium nanoparticles and nanoscale metal or metalloid is about +/−20% of the stoichiometric ratio. In some embodiments, the molar ratio of the total molar of one or more second oxides over the magnesium nanoparticles and nanoscale metal or metalloid is about +/−20% of the stoichiometric ratio.
In some embodiments, the weight percent of the nanoscale metal or metalloid of the total weight of the composition is about 9.0% to about 10.5%.
In some embodiments, the weight percent of the magnesium nanoparticles of the total weight of the composition is about 0.5% to about 4.0%.
Another aspect of the disclosure provided herein relates to a method of fabricating the composition disclosed herein. The method comprises dispersing the magnesium nanoparticles, the nanoscale metal or metalloid, and the oxidizer in a first solvent to provide a first composition, and drying the first composition to provide the composition.
In some embodiments, the first solvent is an organic solvent that does not contain oxygen, or a mixture of multiple organic solvents that do not contain oxygen.
In some embodiments, the dispersing step comprises ultrasonication of the mixture to provide a homogeneous composition.
Techniques, systems and apparatus are described for fabricating magnesium-based composites. In particular, a composite includes a combination of magnesium nanoparticles and boron and/or copper oxide.
Those and other aspects and associated implementations and benefits of the disclosed technology are described in greater detail in the drawings, the description and the claims.
This application contains at least one drawing executed in color. Copies of this application with color drawing(s) will be provided by the Office upon request and payment of the necessary fees.
As used in the specification and claims, the singular form “a,” “an,” and “the” includes plural references unless the context clearly dictates otherwise. It should be understood that the terms “a” and “an” as used herein refer to “one or more” of the enumerated components.
The use of the alternative (e.g., “or”) should be understood to mean either one, both, or any combination thereof of the alternatives.
The term “about” as used herein in the context of a number refers to a range centered on that number and spanning 10% less than that number and 10% more than that number. The term “about” used in the context of a range refers to an extended range spanning 10% less than that the lowest number listed in the range and 10% more than the greatest number listed in the range.
Throughout this disclosure, any concentration range, percentage range, ratio range, or integer range is to be understood to include the value of any integer within the recited range and, when appropriate, fractions thereof (such as one tenth and one hundredth of an integer), unless otherwise indicated. Also, any number range of this disclosure relating to any physical feature, such as polymer subunits, size, or thickness, are to be understood to include any integer within the recited range, unless otherwise indicated. Throughout this disclosure, numerical ranges are inclusive of their recited endpoints, unless specifically stated otherwise.
Unless the context requires otherwise, throughout the present specification and claims, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is, as “including, but not limited to.” As used herein, the terms “include” and “comprise” are used synonymously.
Unless specified otherwise, the terms “composition” and “composite” may be used interchangeably.
Unless specified otherwise, the term “fuel” refers to the metal and metalloid of a composition disclosed herein. For example, for a composition comprising Mg nanoparticles, a nanoscale metal or metalloid, and an oxidizer, the term “fuel” refers to Mg nanoparticles and the nanoscale metal or metalloid.
Nanoscale metals and metalloids such as aluminum (Al), titanium (Ti), magnesium (Mg), boron (B), and silicon (Si), have been explored as high-energy fuels in nanoenergetic composites for propellant and pyrotechnic applications. Among these fuels, boron is regarded as the premier candidate fuel due to its higher gravimetric and volumetric reaction enthalpies, as shown in
As shown in the Examples provided herein, the incorporation of Mg nanoparticles (NPs) in embodiments of boron/copper(II) oxide (B/CuO) thermite compositions (Example 1) and in Ti/CuO thermite compositions (Example 3) both resulted in higher reactivities. For example, when compared to the corresponding thermite compositions without Mg NPs, the pressurization rates of the Mg-present thermite compositions were enhanced to about 6-fold higher (
The mechanism of the reaction between Mg and B2O3 particles was probed through a combination of differential scanning calorimetry (DSC), reaction product characterization, and high-speed time-of-flight mass spectrometry (T-jump/TOFMS). These characterizations revealed that the mechanism of the Mg—B2O3 interaction may involve an exothermic redox reaction between vapor-phase Mg and molten B2O3, without wishing to be bound by the mechanism. For example, Mg vapor may undergo one or more heterogeneous reactions with molten B2O3 shell of boron at relatively low temperatures. These surface reactions may occur prior to the ignition of B with CuO and may cause surface disruptions in the oxide shell, resulting in the observed enhanced reactivity of B-composites, without wishing to be bound by the mechanism.
Magnesium nanoparticles also showed similar exothermic redox reactions with Al2O3, TiO2, and SiO2 (Table 3). Adding Mg to other nanoscale fuels (e.g., Al, and Si) may also result in a similar enhancement in their energy release by reacting with their oxide shell.
Magnesium nanoparticles, as an additive fuel, may offer a thermodynamically and kinetically viable source of a highly reactive gas-phase Mg that can potentially act as an etchant for the oxide shell of metal or metalloid in a thermite composition, without wishing to be bound by the mechanism.
One aspect of the disclosure provided herein relates to a composition comprising magnesium nanoparticles, a nanoscale metal or metalloid, and an oxidizer. When compared to a second composition comprising the same amount of the oxidizer and the nanoscale metal or metalloid but without the magnesium nanoparticles, the composition may have one or more advantages selected from the following: a) a reduced burn time (e.g., reduced by about 50% to about 70%, and/or by about 2.0 ms to about 5.0 ms); b) an increased pressurization rate (e.g., increased by about 5-fold to about 6-fold); c) an increased peak pressure (e.g., increased by about 15% to about 30%); and d) a lower ignition temperature (e.g., an ignition temperature of about 500° C. to about 750° C.).
Examples of the metal or metalloid include, without limitation, boron, silicon, aluminum, and titanium.
In some embodiments, the composition comprises magnesium nanoparticles, a nanoscale metal or metalloid, and an oxidizer, wherein the composition has a burn time reduced by about 50% to about 70% when compared to a second composition comprising the same amount of the oxidizer and the nanoscale metal or metalloid but without the magnesium nanoparticles. In certain embodiments, the burn time is reduced by about 1.0 ms to about 10.0 ms, about 1.5 ms to about 10.0 ms, about 2.0 ms to about 10.0 ms, about 2.5 ms to about 10.0 ms, about 3.0 ms to about 10.0 ms, about 3.5 ms to about 10.0 ms, about 4.0 ms to about 10.0 ms, about 4.5 ms to about 10.0 ms, about 5.0 ms to about 10.0 ms, about 5.5 ms to about 10.0 ms, about 6.0 ms to about 10.0 ms, about 6.5 ms to about 10.0 ms, about 7.0 ms to about 10.0 ms, about 1.0 ms to about 9.0 ms, about 1.5 ms to about 9.0 ms, about 2.0 ms to about 9.0 ms, about 2.5 ms to about 9.0 ms, about 3.0 ms to about 9.0 ms, about 3.5 ms to about 9.0 ms, about 4.0 ms to about 9.0 ms, about 4.5 ms to about 9.0 ms, about 5.0 ms to about 9.0 ms, about 5.5 ms to about 9.0 ms, about 6.0 ms to about 9.0 ms, about 6.5 ms to about 9.0 ms, about 7.0 ms to about 9.0 ms, about 1.0 ms to about 8.0 ms, about 1.5 ms to about 8.0 ms, about 2.0 ms to about 8.0 ms, about 2.5 ms to about 8.0 ms, about 3.0 ms to about 8.0 ms, about 3.5 ms to about 8.0 ms, about 4.0 ms to about 8.0 ms, about 4.5 ms to about 8.0 ms, about 5.0 ms to about 8.0 ms, about 5.5 ms to about 8.0 ms, about 6.0 ms to about 8.0 ms, about 6.5 ms to about 8.0 ms, about 7.0 ms to about 8.0 ms, about 1.0 ms to about 7.0 ms, about 1.5 ms to about 7.0 ms, about 2.0 ms to about 7.0 ms, about 2.5 ms to about 7.0 ms, about 3.0 ms to about 7.0 ms, about 3.5 ms to about 7.0 ms, about 4.0 ms to about 7.0 ms, about 4.5 ms to about 7.0 ms, about 5.0 ms to about 7.0 ms, about 5.5 ms to about 7.0 ms, about 6.0 ms to about 7.0 ms, about 1.0 ms to about 8.5 ms, about 1.0 ms to about 7.5 ms, about 2.0 ms to about 5.0 ms, about 4.5 ms, or about 2 ms. In certain embodiments, the burn time is reduced by at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or any ranges there between.
In some embodiments, the composition comprises magnesium nanoparticles, a nanoscale metal or metalloid selected from the group consisting of boron, silicon, aluminum, and titanium, and an oxidizer, wherein the composition has a pressurization rate increased by about 5 fold to about 6 fold when compared to a second composition comprising the same amount of the oxidizer and the nanoscale metal or metalloid but without the magnesium nanoparticles. In certain embodiments, the pressurization rate is increased by at least about 1 fold, at least about 2 fold, at least about 3 fold, at least about 4 fold, at least about 5 fold, at least about 6 fold, at least about 7 fold, at least about 8 fold, at least about 9 fold, at least about 10 fold, or any ranges therebetween.
In some embodiments, the composition comprises magnesium nanoparticles, a nanoscale metal or metalloid selected from the group consisting of boron, silicon, aluminum, and titanium, and an oxidizer, wherein the composition has a peak pressure increased by about 15% to about 30% when compared to a second composition comprising the same amount of the oxidizer and the nanoscale metal or metalloid but without the magnesium nanoparticles. In certain embodiments, the peak pressure is increased by at least about 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, or any ranges therebetween.
In some embodiments, the composition comprises magnesium nanoparticles, a nanoscale metal or metalloid selected from the group consisting of boron, silicon, aluminum, and titanium, and an oxidizer, wherein the composition has a lower ignition temperature when compared to a second composition comprising the same amount of the oxidizer and the nanoscale metal or metalloid but without the magnesium nanoparticles. In certain embodiments, the ignition temperature is lowered by at least about 50° C., at least about 75° C., at least about 100° C., at least about 125° C., at least about 150° C., at least about 175° C., at least about 200° C., or any ranges therebetween. In certain embodiments, the ignition temperature is about 500° C. to about 750° C., lower than about 750° C., lower than about 700° C., lower than about 650° C., lower than about 600° C., lower than about 550° C., or about 500° C., or any ranges therebetween.
In some embodiments, the oxidizer comprises a first oxide of the metal or metalloid. In some embodiments, the first oxide of the metal or metalloid is a native oxide shell of the metal or metalloid. In some embodiments, the first oxide of the metal or metalloid may further comprise oxides that are not the native oxide shell of the metal or metalloid.
In some embodiments, the oxidizer comprises one or more second oxides other than the oxides of the metal or metalloid. Examples of the one or more second oxides include, without limitation, CuO, B2O3, SiO2, TiO2, and Al2O3.
In some embodiments, the oxidizer may be oxygen.
In some embodiments, the nanoscale metal or metalloid has an average particle size of no more than about 100 nm, no more than about 120 nm, no more than about 140 nm, no more than about 160 nm, no more than about 180 nm, no more than about 200 nm, no more than about 220 nm, no more than about 240 nm, no more than about 260 nm, no more than about 280 nm, no more than about 300 nm, no more than about 310 nm, no more than about 320 nm, no more than about 330 nm, no more than about 340 nm, no more than about 350 nm, no more than about 360 nm, no more than about 370 nm, no more than about 380 nm, no more than about 390 nm, no more than about 400 nm, no more than about 410 nm, no more than about 420 nm, no more than about 430 nm, no more than about 440 nm, no more than about 450 nm, no more than about 475 nm, no more than about 500 nm, no more than about 525 nm, no more than about 550 nm, no more than about 575 nm, no more than about 600 nm, no more than about 650 nm, no more than about 700 nm, no more than about 750 nm, no more than about 800 nm, no more than about 850 nm, no more than about 900 nm, no more than about 950 nm, no more than about 1000 nm, or any combination of values establishing a range thereof. For example, in some embodiments, the nanoscale metal or metalloid has an average particle size of about 390 nm to about 420 nm.
In some embodiments, the magnesium nanoparticles have an average particle size of no more than about 100 nm, no more than about 120 nm, no more than about 140 nm, no more than about 160 nm, no more than about 180 nm, no more than about 200 nm, no more than about 220 nm, no more than about 240 nm, no more than about 260 nm, no more than about 280 nm, no more than about 300 nm, no more than about 310 nm, no more than about 320 nm, no more than about 330 nm, no more than about 340 nm, no more than about 350 nm, no more than about 360 nm, no more than about 370 nm, no more than about 380 nm, no more than about 390 nm, no more than about 400 nm, no more than about 410 nm, no more than about 420 nm, no more than about 430 nm, no more than about 440 nm, no more than about 450 nm, no more than about 475 nm, no more than about 500 nm, no more than about 525 nm, no more than about 550 nm, no more than about 575 nm, no more than about 600 nm, no more than about 650 nm, no more than about 700 nm, no more than about 750 nm, no more than about 800 nm, no more than about 850 nm, no more than about 900 nm, no more than about 950 nm, no more than about 1000 nm, or any combination of values establishing a range thereof. For example, in some embodiments, the magnesium nanoparticles have an average particle size of about 350 nm to about 400 nm.
In some embodiments, the molar of the magnesium nanoparticles over the total molar of the magnesium nanoparticles and the nanoscale metal or metalloid ranges is at least about 1.5%, at least about 2.0%, at least about 2.5%, at least about 3.0%, at least about 3.5%, at least about 4.0%, at least about 4.5%, at least about 5.0%, at least about 6.0%, at least about 7.0%, at least about 8.0%, at least about 9.0%, at least about 10.0%, at least about 11.0%, at least about 12.0%, at least about 13.0%, at least about 14.0%, at least about 15.0%, at least about 16.0%, at least about 17.0%, at least about 18.0%, at least about 19.0%, at least about 20.0%, at least about 21.0%, at least about 22.0%, at least about 23.0%, at least about 24.0%, at least about 25.0%, at least about 26.0%, at least about 27.0%, at least about 28.0%, at least about 29.0%, at least about 30.0%, or any combination of values establishing a range thereof. For example, in some embodiments, the molar of the magnesium nanoparticles over the total molar of the magnesium nanoparticles and the nanoscale metal or metalloid is about 3.0% to about 15.0%.
In some embodiments, the molar ratio of the nanoscale metal or metalloid over the oxidizer is about +/−20%, about +/−15%, about +/−10%, or about +/−5% of the stoichiometric ratio. In some embodiments, the molar ratio of the nanoscale metal or metalloid over the total molar of one or more second oxides is about +/−20%, about +/−15%, about +/−10%, or about +/−5% of the stoichiometric ratio.
In some embodiments, the molar ratio of the magnesium nanoparticles and nanoscale metal or metalloid over the oxidizer is about +/−20%, about +/−15%, about +/−10%, or about +/−5% of the stoichiometric ratio. In some embodiments, the molar ratio of the magnesium nanoparticles and nanoscale metal or metalloid over the total molar of one or more second oxides is about +/−20% of the stoichiometric ratio.
In some embodiments, the molar ratio of the oxidizer over the nanoscale metal or metalloid is about +/−20%, about +/−15%, about +/−10%, or about +/−5% of the stoichiometric ratio. In some embodiments, the molar ratio of the total molar of one or more second oxides over the nanoscale metal or metalloid is about +/−20%, about +/−15%, about +/−10%, or about +/−5% of the stoichiometric ratio.
In some embodiments, the molar ratio of the oxidizer over the magnesium nanoparticles and nanoscale metal or metalloid is about +/−20%, about +/−15%, about +/−10%, or about +/−5% of the stoichiometric ratio. In some embodiments, the molar ratio of the total molar of one or more second oxides over the magnesium nanoparticles and nanoscale metal or metalloid is about +/−20% of the stoichiometric ratio.
In some embodiments, the weight percent of the nanoscale metal or metalloid of the total weight of the composition is about 9.0% to about 10.5%.
In some embodiments, the weight percent of the magnesium nanoparticles of the total weight of the composition is about 0.5% to about 4.0%.
Another aspect of the disclosure provided herein relates to a method of fabricating the composition disclosed herein.
In certain embodiments, the method comprises dispersing the magnesium nanoparticles, the nanoscale metal or metalloid, and the oxidizer in a first solvent to provide a first composition, and drying the first composition to provide the composition.
In some embodiments, the first solvent is an organic solvent that does not contain oxygen, or a mixture of multiple organic solvents that do not contain oxygen. Examples of the first solvent includes, without limitation, aliphatic hydrocarbons (e.g., alkanes, alkenes, and alkynes), aromatic hydrocarbons (e.g., benzene, toluene), hydrocarbons substituted with one or more halogens (e.g., F, Cl, Br, I), such as dichloromethane, chloroform, and hydrocarbons substituted with one or more amino groups. In some embodiments, the first solvent is hexane.
In some embodiments, the dispersing step comprises ultrasonication of the mixture to provide a homogeneous composition.
In certain embodiments, the method comprises incorporating Mg nanoparticles into a third composition comprising the nanoscale metal or metalloid and the oxidizer.
One specific embodiment of the fabrication process 300 is depicted in
The following examples are intended to illustrate various embodiments of the invention. As such, the specific embodiments discussed are not to be constructed as limitations on the scope of the invention. It will be apparent to one skilled in the art that various equivalents, changes, and modifications may be made without departing from the scope of invention, and it is understood that such equivalent embodiments are to be included herein. Further, all references cited in the disclosure are hereby incorporated by reference in their entirety, as if fully set forth herein, to the extent that they do not contradict or are not inconsistent with the instant disclosure.
Boron has offered great promise as a candidate fuel in high-energy composites due to its high gravimetric and volumetric energy content, however, its oxidation rate is limited by sluggish diffusion of reactive species across its low-melting oxide shell. On the other hand, Mg nanoparticles (NPs) have been shown recently to undergo rapid vaporization (˜100 us). This release of vapor-phase Mg can potentially be exploited to react exothermically (AH,=−420 KJ/mol) with the B2O3 layer on boron, aiding in surface disruption. Mg NPs were evaluated as an additive fuel to B/CuO nanoenergetic composites. The incorporation of Mg as an additive fuel in B/CuO composites yielded a ˜6-fold enhancement in reactivity with a ˜60% reduction in burn time. Through thermal and reaction product analysis along with high-speed mass spectrometry (T-jump/TOFMS) and ignition characterization, the reaction mechanism of Mg/B2O3 particles as a simulant system for the interaction of Mg with the B2O3 shell of boron was investigated. These characterizations revealed that exothermic heterogeneous reactions occur between vapor-phase Mg and molten B2O3 shell of boron at ˜500-650° C.
Nanoscale metals and metalloids such as Al, Ti, Mg, B, and Si, have been explored as high-energy fuels in nanoenergetic composites for propellant and pyrotechnic applications. Among these fuels, boron has always been regarded as the premier candidate fuel due to its higher gravimetric and volumetric reaction enthalpies, as shown in
Binary fuel systems were explored through the incorporation of energy-dense metal additives such as Al, Mg, and Ti, in boron powders to accelerate B oxidation while maintaining a high energetic content. Employing similar dual fuel systems has been used to control and modulate the transport processes and ignition in thermite mixtures. Among the metal additives explored so far, Mg is particularly attractive due to its high volatility and reactivity. Reducing particle size of Mg NPs could result in their rapid vaporization and a fast vapor-phase Mg release (release timescale ˜ 100 μs at a heating rate of 105° C./s). Additionally, due to the highly negative formation energies of MgO compared to B2O3 (Mg lies lower than B in the Ellingham diagram), the reaction between Mg and B2O3 may be thermodynamically feasible with a reaction enthalpy (AH,) of ˜−420 KJ/mol or −2.9 KJ/g. Mg NPs, as an additive fuel, was tested to offer a thermodynamically and kinetically viable source of a highly reactive gas-phase Mg that may potentially act as an etchant for the oxide shell of boron according to the following reaction:
3Mg+B2O3→3MgO+B,ΔHr=−420 kj/molreaction
Previous studies have reported that coating boron with materials (e.g., fluorographene and fluoroalkylsilanes) that can release gas-phase fluorine species to etch with the B2O3 shell promotes its ignition and combustion. Without wishing to be bound by the mechanism, nanoscale Mg tested herein appeared to provide advantages by generating reactive gas-phase species (Mg vapor) to corrode the oxide shell while maintaining a high energy density of the composites. Although prior studies have explored the role of Mg as an additive in B-based powders, those reports were limited to micron-scale Mg powders that, due to their low surface area, may have slow vaporization and release kinetics of gas-phase Mg species. Furthermore, it was unexpected to observe the synergistic effects of the surface reaction of Mg vapor directly with the oxide shell of boron provided herein.
The energy release characteristics of B/CuO composites with Mg NPs (˜370 nm) incorporated as an additive fuel with loadings ranging from ˜3-15 mol % of the total fuel were fabricated and evaluated. It was demonstrated that incorporating Mg in B/CuO thermite resulted in up to 6-fold higher pressurization rates and ˜60% reduction in burn times of the composites. Through a combination of differential scanning calorimetry (DSC), reaction product characterization, and high-speed time-of-flight mass spectrometry (T-jump/TOFMS), the mechanism of the reaction between Mg and B2O3 particles was probed. These characterizations revealed that the mechanism of the Mg—B2O3 interaction involves an exothermic redox reaction between vapor-phase Mg and molten B2O3.
Boron (˜410 nm as measured from the SEM in
The active content of B NPs was determined by performing TGA in an O2 atmosphere at 1200° C. for ˜80 min, as shown in
2Mg+O2→2MgO
4B+302→2B2O3
The active content for B and Mg obtained from the TGA mass gain were calculated to be ˜80% and ˜88%, respectively.
Boron oxide (B2O3) was purchased from Alfa Aesar, and was ball milled to reduce the particle size to ˜2 μm.
To reduce the particle size of B2O3 purchased from Alfa Aesar, a ball milling procedure was employed. Briefly, ˜200 mg B2O3 and 1 mL hexane were added into a 2 mL centrifuge tube, followed by addition of 3 hardened steel and alumina balls (purchased from GlenMills, 7/32″ in diameter). The tube was then loaded into a Retsch CryoMill operated at ambient conditions for milling (frequency of 25.0 Hz) for a total of 180 min with 18 cycles to avoid heat accumulation (one cycle was 10 min and interval between cycles was at least 5 min). More hexane was added during the process to maintain a roughly constant volume of hexane in the centrifuge tube. The milled samples were then collected and dried in vacuum oven at 150° C. for ˜5 h. The average size of the particles was ˜2 μm.
The B—Mg/CuO nanothermite composites were prepared by adding the fuel and oxidizer components in hexane (10 mg/mL solid loading) followed by ˜1h of ultrasonication to achieve homogeneous particle mixing. The samples were then dried for 24 hours under ambient conditions to obtain the thermite powders. For these composites, incremental amounts of Mg particles were added while a constant B/CuO mass ratio was maintained to achieve a fuel:oxidizer equivalence ratio of 1 (B/CuO, ϕ=1). The composition of the formulations fabricated have been tabulated in Table 1.
Constant-volume combustion cell (˜20 cm−3) characterization was performed on 25.0 mg of the samples using the setup as described in Ghildiyal et al. ACS Appl. Mater. Interfaces 14(15) 17164-17174, 2022 and Ghildiyal et al. ACS Appl. Mater. Interfaces 13(1) 458-467, 2021.
Microscopic characterization of the samples was performed on an FEI NNS450 microscope operating at 18 kV. The nanoparticle structure and composition were characterized with an FEI Titan Themis 300 scanning transmission electron microscope (300 kV) with a high-angle annular dark-field detector (HAADF). Constant-volume combustion cell (˜20 cm3) measurements were performed on 25.0 mg of the fabricated thermite composites using a setup described in our previous studies. For thermogravimetric analysis and differential scanning calorimetry (TGA/DSC), a Netsch STA449 F3 Jupiter thermal analyzer was used. Ultrahigh purity argon (purity ˜99.9999%) was used as the TGA atmosphere to prevent Mg particle oxidation. X-ray diffraction on the samples was performed with a PANanalytical Empyrean Series 2 diffractometer (Cu Ka radiation). Attenuated total reflection-Fourier transform infrared (ATR-FTIR) characterization on the samples was performed on a Nicolet iS50R spectrometer with a deuterated triglycine sulfate (DTGS) detector with a 4 cm−1 resolution. Crushed and dried KBr was used as a reference, and the spectra obtained were processed using Happ-Genzel apodization, Mertz phase correction, and atmospheric suppression.
T-Jump/TOFMS and ignition temperature characterizations were performed to probe and investigate the reaction mechanisms in the fabricated composites at high heating rates (˜105 K s−1), as detailed in Ghildiyal et al. ACS Appl. Mater. Interfaces 13(1) 458-467, 2021 and Delisio et al. J. Phys. Chem. 120(24), 5534-5542, 2016. Briefly, a small quantity (˜5 mg) of the prepared composites were dispersed in hexane and sonicated for ˜10 min. The suspension was then drop cast on a platinum wire (˜1 cm, 76 μm diameter) soldered to copper leads of the electrical feedthroughs. The samples were then heated with a ˜3 ms pulse under a high vacuum (10° atm) to a maximum temperature of ˜1400 K. Following thermal activation by the pulse, the gas-phase species evolved during the reaction were ionized with a 70-eV electron gun and probed with a multichannel plate detector for 10 ms with a temporal resolution of 100 μs. The ignition characterization of the samples was carried out with a high-speed camera (Vision Research Phantom v12.0) in an argon environment at 1 atm pressure. The ignition point was identified by correlating the optical emission obtain from the camera with the time and temperature obtained from wire heating.
The effect of Mg NPs as an additive fuel on the reactivity and energy release of boron NP-based composites was explored. To evaluate this effect, B/Mg/CuO nanoenergetic composites were fabricated with varying additive content of Mg NPs, and their pressurization characteristics were characterized by constant-volume combustion cell measurements, as described in Ghildiyal et al. ACS Appl. Mater. Interfaces 14(15) 17164-17174, 2022.
Based on these observations, the reactivity enhancement in Mg/B samples relative to Mg— or B-based composites suggested a synergistic effect between Mg and B fuels was likely responsible for the augmentation observed in
The reaction mechanism of the Mg/B2O3 reaction was investigated to probe this reaction and its implications on reactivity enhancement of B NPs, as Mg/B2O3 was a simulant for the interaction of Mg with the oxide shell of boron (B2O3). Mg/B2O3 composites were fabricated assuming a stoichiometric redox reaction between the components (ϕ=1) and their constant-volume pressurization and ignition characteristics were evaluated. As shown in
Mg/B2O3 Reaction Mechanisms: Ignition, Thermal Analysis, and Reaction Product Characterization
The reactions and the associated thermochemistry potentially involved in the B/Mg/CuO thermite system are summarized in Table 2. The reaction of Mg with CuO and B2O3 are energetically comparable both on a gravimetric and a molar basis as seen in Table 2.
Although the contribution from the Mg/CuO reaction cannot be completely neglected, it was noted that thermodynamically, Mg has relatively similar molar and gravimetric reaction enthalpies with both CuO and B2O3, as shown in Table 2. Moreover, the lower ignition temperature and early reaction onset for the Mg/B2O3 mixture than Mg/CuO and B/CuO thermites suggested that Mg could initiate the reaction with the oxide layer of B much earlier than its ignition and combustion with CuO. In the case of aluminum, pre-ignition reactions with its oxide shell (Al2O3) with reactive gases (e.g., HF, F2) have been shown to significantly affect their combustion. Therefore, the low temperature, pre-ignition Mg/B2O3 surface reactions may play a significant role in surface disruption and reactivity enhancement of boron.
To further characterize the reaction between Mg and B2O3 thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) and x-ray diffraction (XRD) analysis were performed on the Mg/B2O3 mixtures to further characterize the reaction between Mg and B2O3.
Step I: 3Mg+B2O3→3MgO+B
Step II: 3MgO+B2O3→Mg3B2O6
The Mg/B2O3 redox reaction was further corroborated by the absence of BOX (BO3/BO4), O—H, and B—O—B peaks in the FTIR spectra of the Mg/B2O3 mixtures heated at 650° C., as shown in
Mg/B2O3 Reaction Mechanism: T-Jump/TOFMS and Implications on Oxide Shell Disruption of B NPs
To further probe the interaction between Mg and B2O3, the species evolved from thermally activated Mg/B2O3 reaction at a high heating rate (105 K/s) using T-jump/TOFMS were analyzed.
In order to investigate the effect of Mg directly on the B2O3 oxide layer of boron NPs, a mixture of Mg and B NPs (˜10 mol % of Mg relative to total mixture) was prepared without any oxidizer, and DSC characterization was performed on the sample in ultrahigh purity argon.
The reaction mechanisms of the Mg/B2O3 system to Mg/B NP-based composites can be extrapolated, whereby Mg vapor reacts with the molten B2O3 shell, as illustrated in
The XRD patterns of the powders, shown in
Lastly, the exothermic reactions may also increase the local temperature of the unreacted B2O3 shell, and assist in its physical vaporization and removal, thereby contributing to the reaction rate enhancement of boron particle oxidation. Prior studies have observed that reactive gas-phase species that can react with the B2O3 shell may assist in its removal and lead to enhanced boron combustion. Assuming a 50% reaction between Mg and B2O3 shell, and further assuming the exothermicity of the reaction is localized on the oxide shell (neglecting all heat losses), a simple energy balance yields an extremely high local surface temperature (T ˜3200° C. >boiling point of B2O3 ˜1860).
The surface temperature of the oxide layer of B NPs due to its reaction with Mg vapor was estimated according to the following redox reaction:
3Mg+B2O3→3MgO+B ΔHr=−420 kJ/mol
Assuming 50 mol % of the B2O3 was consumed by the Mg and the heat released was localized on the remnant oxide shell of boron particles, the local temperature increase could be estimated according to the following equation:
where ΔTox was the temperature rise of the remaining B2O3 layer, ΔH, was the heat generated from the reaction of 50 mol % of B2O3 with Mg (ΔHox=1.3×10-17 J), mox. was the mass of the oxide layer (=3.6×10−18 kg, thickness ˜5 nm), Cp, ox was the specific heat capacity of the oxide layer (=129.6 J mol−1° C.−1).
Using these values, the estimated temperature increase of the B2O3 layer was ˜3200° C. Note that these values were obtained without considering any heat losses in the system.
Of course, the actual temperature of the shell may be considerably lower than this value due to the heat losses involved. Nevertheless, the estimates and the observations above suggested that the Mg/B2O3 (oxide shell) reaction system possessed sufficient energy required for the vaporization of the molten B2O3 layer. These results indicated that additional surface reactions relating to the interaction of Mg with the oxide shell of boron particles contributed significantly to their reactivity enhancement.
Nanoscale reactive metals and metalloids such as Al, Ti, and Si are attractive commercially available fuels for nanoenergetic composites due to their high energy densities. However, the inert native oxide shells on the surfaces of these fuels (Al2O3, TiO2, and SiO2) present kinetic diffusional barriers to reactive species, hindering their oxidation and energy. The inert oxide layer adds dead mass to the energetic mixture and reduces their overall energy content. Nanoscale Mg has been shown to undergo rapid vaporization, releasing highly reactive Mg vapor which can corrode the surface of boron nanoenergetic composites by reacting exothermically with its B2O3 layer, resulting in enhanced burn characteristics. Since Mg also shows similar exothermic redox reactions with Al2O3, TiO2, and SiO2 (as shown in Table 3), adding Mg to other nanoscale fuels (nAl/nTi/nSi) may show a similar enhancement in their energy release and total by reacting with their oxide shell.
Mg NPs were prepared as described in Example 1. Unless specified otherwise, experiments were performed similarly to those described in Example 1. The active content of the fuels (Ti, Al, Si, and Mg) were estimated from the mass gain upon oxidation in air or O2. Nanopowers of titanium oxide (TiO2), silicon oxide (SiO2), and aluminum oxide (Al2O3) were purchased from commercially available sources, and were used as received.
As shown in
The Mg—Ti/CuO nanothermite composites were prepared by adding the fuel and oxidizer components in hexane (10 mg/mL solid loading) followed by ˜1h of ultrasonication to achieve homogeneous particle mixing. The samples were then dried for 24 hours under ambient conditions to obtain the thermite powders. For these composites, incremental amounts of Mg particles were added while a constant Ti/CuO mass ratio was maintained to achieve a fuel:oxidizer equivalence ratio of 1 (Ti/CuO, ϕ=1). Constant-volume combustion cell (˜20 cm−3) characterization was performed on 25.0 mg of the samples using the setup described in prior works.
Unless specified otherwise, experiments were performed similarly to those described in Example 1. Preliminary results with additive amounts of Mg to Ti/CuO mixtures showed an enhancement in pressurization and burn characteristics, as shown in
While this specification contains many specifics, these should not be construed as limitations on the scope of an invention or of what may be claimed, but rather as descriptions of features specific to particular embodiments of the invention. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or a variation of a subcombination.
Only a few implementations are disclosed. However, variations and enhancements of the disclosed implementations and other implementations can be made based on what is described and illustrated in this specification.
References listed below and included herein are incorporated by reference in their entirety.
This patent document claims the benefits and priority to U.S. Provisional Patent Application No. 63/386,561, filed on Dec. 8, 2022, which is incorporated herein by reference in its entirety.
This invention was made with government support under Contract No. N00014-21-1-2038 awarded by the Office of Naval Research. The Government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 63386561 | Dec 2022 | US |
